America said: "I portray his wife Helen, and what was so exciting was to show the complexity of her role, not only as his wife and homemaker but in the [civil rights] movement. She was out there in the thick of the strike, getting arrested, working to get money. It's such a pleasure to make sure the stories about women and the role they played in history doesn't go unnoticed."

The actress also voices independent young princess Astrid in animated sequel How To Train Your Dragon 2. And she revealed why she thinks it's important to provide children with good role models in films, even from such a young age.

She said: "I am so aware of how it shaped me, the characters and stories and possibilities I was exposed to.

"I think more and more, the younger generation are shaped by the media and the messages sent to them. I know people like to talk it down and say we [actors and film-makers] are not changing lives, but we are. We're deciding what, as a society, we're going to accept as our standards and limitations.

"And with a special movie like this, which is going to be watched by kids, we need to shape the world for them, so it is important and it does matter.

"As a young girl I wanted to be 'doing'. I wanted to be out in the world being the hero of my own story, not the princess in some other hero's story. And I think the reason projects with empowering female characters are being devoured is because it's long overdue.

"Girls can be the centre of their stories and not be waiting around to be saved. It's what I wanted to watch as a child, what I want to do as an adult and what I want to see, so I do gravitate towards those roles that are about being your own hero."